Howdy people, I am a diy virgin so please be gentle. I always wanted a tube amp like a mac275 etc but nice ones are a small fortune. So while surfing ebay one day I am lured bya chinese amp. I couldn't help myself. The place was going out of business in hong kong so I bought four. One week later they showed up. They look very nice but two of them came with no tubes. They should be 4 KT88 2 12AT7 and 2 12AU7. I know nothing. I have read that after going through the amps to make sure they are made correctly that tube rolling is good for 5% improvement. Anyway my question is what tubes would you guys recomend. And are tube numbers the same. Like does a KT88 have an equivalent with a different number? Oh the amps are music angel Kt88, mengyue mini and a meng mini headphone amp. Thanks Tom
12AT7 and 12AU7 are common tubes, and should be easy to find. Unused old stock tubes will cost a lot. New production tubes are cheap and plentiful. You may find JAN (joint army-navy) substitutes for most of the 12A?7 series. For example, the JAN 5814 is interchangeable with the 12AU7.
You can probably substitute the 6550 for the KT88. New production KT88 will probably cost between $100 and $200 for a set of four. I've heard nothing but good reports on the New Sensor "Genalex" re-issues:
http://newsensor.com/ProductHighLight.aspx?ProId=1149
Old stock KT88 (GEC or original Genalex Gold Lion) will cost more than a small fortune. Old stock GE6550A are also supposed to be very good, and any would-be owners will have to pay dearly for them.
You can probably substitute the 6550 for the KT88. New production KT88 will probably cost between $100 and $200 for a set of four. I've heard nothing but good reports on the New Sensor "Genalex" re-issues:
http://newsensor.com/ProductHighLight.aspx?ProId=1149
Old stock KT88 (GEC or original Genalex Gold Lion) will cost more than a small fortune. Old stock GE6550A are also supposed to be very good, and any would-be owners will have to pay dearly for them.
Selection
Hi Tom:
The choices on tube selection for your amp are numerous..fortunately.
There is two basic choices, new or "Old", the old stuff is very good as compared to the new stuff, The prices are jacked up according to the percieved quality of the old stuff. The more common old stuff is priced very reasonable. The lifetimes rated in hours of operation is very high (EG. 30,000 Hrs.) , so a 'worn out' tube is rather unlikely.
The new stuff is primarily made overseas with Russia and the baltic states being the leader in production. The reason for this is the old USSR had and still uses tube gear in applications where in the US would have been replaced with solid state long ago. Even some U.S. companies have relocated to these factories in said locales as they have the machining and experience building tubes.
The old adage still applies "You get what you pay for"
Me.. I would get the "old" stuff as they have a proven track record.
_______________________________________Rick........
Hi Tom:
The choices on tube selection for your amp are numerous..fortunately.
There is two basic choices, new or "Old", the old stuff is very good as compared to the new stuff, The prices are jacked up according to the percieved quality of the old stuff. The more common old stuff is priced very reasonable. The lifetimes rated in hours of operation is very high (EG. 30,000 Hrs.) , so a 'worn out' tube is rather unlikely.
The new stuff is primarily made overseas with Russia and the baltic states being the leader in production. The reason for this is the old USSR had and still uses tube gear in applications where in the US would have been replaced with solid state long ago. Even some U.S. companies have relocated to these factories in said locales as they have the machining and experience building tubes.
The old adage still applies "You get what you pay for"
Me.. I would get the "old" stuff as they have a proven track record.
_______________________________________Rick........
The continuing saga of my chinese amp purchase. Well the two big KT88's came with no tubes. So I moved on to the mengyue mini el84 15w per amp. It blew the fuse at power up. Argh! So I'm 0 for 3. Then I hooked up the mengyue mini headphone amp and it actually works! Sounds pretty good too. So much for the great deal.
I've been using JJ 12AX7S's and 12AU7's and never had a complaint. They're dead quiet with no humming or hissing. Excellent sound from top to bottom, with no glare, coloration or harshness. The best part is they're inexpensive ($10.00) and you can get them balanced and matched for only $4.00 more at TubeDepot.
For KT-88's I use Electro Harmonix. They've got a deep, powerful bass, highly detailed and realistic mids with absolutely no harshness on top. Very silky. Ive tried JJ's and SED's, but the EH's seem to have a clearer and cleaner top.
And for the EL84 that blows fuses, you may first want to take the bottom cover (with the cord unplugged of course) and check for burned up components. It's probably something really simple.
~~~Johnny~~~
For KT-88's I use Electro Harmonix. They've got a deep, powerful bass, highly detailed and realistic mids with absolutely no harshness on top. Very silky. Ive tried JJ's and SED's, but the EH's seem to have a clearer and cleaner top.
And for the EL84 that blows fuses, you may first want to take the bottom cover (with the cord unplugged of course) and check for burned up components. It's probably something really simple.
~~~Johnny~~~
I had just assumed the electroharmonic tubes were not so great cuz of the reasonable cost. I will now include them in my search. I did pop the bottom cover off of the el84 amp and saw no damage but I didn't pull the circuit board loose to see the other side of it. I didn't pull the transformers either, I'll keep digging. thanks
The continuing saga update
I finally got ahold of the guy who sold me these things. He happily refunded me $220. for the missing tubes. Seeing how I probably would have upgraded them anyway, I'm actually ahead! I paid $46. and $151. for the two amps so now I pretty much got them for free plus shipping. So I ended up buying new cryo treated electro harmonics for $290. If these amps are ok I should be a very happy camper. As for the other el84 amp I think I'll just take it in.
I finally got ahold of the guy who sold me these things. He happily refunded me $220. for the missing tubes. Seeing how I probably would have upgraded them anyway, I'm actually ahead! I paid $46. and $151. for the two amps so now I pretty much got them for free plus shipping. So I ended up buying new cryo treated electro harmonics for $290. If these amps are ok I should be a very happy camper. As for the other el84 amp I think I'll just take it in.
For the EL84 amp, you may want to check the output tubes before you take it to the shop. A few years back, Chinese output tubes had a bad reputation for shorting out. Try putting in another fuse, then pull all the EL84's. If the fuse doesn't blow, it's the tubes. EL84 tubes are very inexpensive these days, and you can get a good quad for $40 or less. If the fuse does blow, it can be something serious, like a shorted power trannie.
~~~John~~~
~~~John~~~
squirtacious said:
Well.. maybe.. maybe not.. some heaters just do that.. glow really bright and then calm down... hard to say.... have you decided what to do? Fix it yourself or get it fixed? I do some repair work.. and that's why I said it before.. Im sure you could find someone on this board to fix it for you.. (not just me mind you... ) If you do choose to do it yourself --- with a digital camera im sure we could all chip in...
-Sean
Just a reminder, Most Chinese amps do not seem to have bleed resistors fitted. If you power up the amp with no tubes fitted then the HT (B+) line may be left fully charged and give quite a nasty surprise. If you are going to go probing, best to check/discharge the B+ with for example a well insulated high watt 100 Ohm resistor.
Play safe, take care.
Les
Play safe, take care.
Les
Chinese tube amp.
recently, I've bought a Chinese tube amp. it's junk, not worth a penny but cost me hundreds of shilling. If you ever bought any equipment manufacturer ed by Chinese, think about Mattel, all the products either returned or discarded, total lost!!!.
They can produced an amplifier by sticking the filter can caps. with hotmelt glue, tubes were digged out from **** yard, ( War in Vietnam between US and China half decade ago ) the wiring is owful and horrible. imagine a messed up spider web. When U power up the unit after half an hour, the tranny gets hot and dissolve the hotmelt which used to position the filter can caps. Then the Hi -voltage terminal of the cap. shorted together and give a " bang ", then followed with a stinky smell like evaporating ***** and urine, this is the result from the heating up tubes digged out from **** yard, after these, smoke in white colour came out from the overheated power transformer, due to the spider web wiring collapsed and cause shorted cct. The tubes socket they used were disassembled from scraped junk yard equipment, thunder and sparking noise generated between the tube and the socket contact when it was working. Such amplifier I still have to paid for the garbage man to remove the unit away. None of the component left can be used. Even the output tranny both were internal partially shorted cause by the reused copper wire. Pocket Tragedy and money lost !!!
If you people want to loose money, consider buy Chinese Amplifiers or their products.
recently, I've bought a Chinese tube amp. it's junk, not worth a penny but cost me hundreds of shilling. If you ever bought any equipment manufacturer ed by Chinese, think about Mattel, all the products either returned or discarded, total lost!!!.
They can produced an amplifier by sticking the filter can caps. with hotmelt glue, tubes were digged out from **** yard, ( War in Vietnam between US and China half decade ago ) the wiring is owful and horrible. imagine a messed up spider web. When U power up the unit after half an hour, the tranny gets hot and dissolve the hotmelt which used to position the filter can caps. Then the Hi -voltage terminal of the cap. shorted together and give a " bang ", then followed with a stinky smell like evaporating ***** and urine, this is the result from the heating up tubes digged out from **** yard, after these, smoke in white colour came out from the overheated power transformer, due to the spider web wiring collapsed and cause shorted cct. The tubes socket they used were disassembled from scraped junk yard equipment, thunder and sparking noise generated between the tube and the socket contact when it was working. Such amplifier I still have to paid for the garbage man to remove the unit away. None of the component left can be used. Even the output tranny both were internal partially shorted cause by the reused copper wire. Pocket Tragedy and money lost !!!
If you people want to loose money, consider buy Chinese Amplifiers or their products.
squirtacious said:I'll bet your right. I did notice one of the input tubes got bright right away then pop! I figured that I would try a new fuse then power up with no tubes. But i didn't think that would prove anything for sure. So I didn't, but now I will. Thanks
This kind of symptom I experienced. Some tube gives bright filiament when lid then dimmed. this because the filiament inside the cathode sleeve partially shorted and back to normal after heated up. If you disassemble a bad tube, ( not filiament failure ) you will see the tungsten wire was very fine and fragile, then wired up in a spring shaped coil, then flipped several times back and forth, usually the short took place between the flipped angles. After heated up, the tungsten wire expanded and released the shorted angle, then the tube becomes normal.
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